The present invention relates to a method and system for generating a signal representative of the transverse movement of a vehicle, utilizing the RPM of at least two wheels of at least one axle.
The maximally accurate knowledge of the movements of a vehicle is of elementary significance for any type of control or regulation which counteracts these movements in the sense of increasing the travel comfort and road safety.
Such a counteraction can be accomplished, as described in DE-OS 35 29 178, by an active suspension and/or damping system whose suspension and/or damping performance is of a controllable or regulable configuration.
Furthermore, such influencing of the vehicle movements may be effected by controllable or regulable allocation of force to the individual drive wheels and/or by controllable or regulable steering operations. In exemplary fashion, reference is made in this context to a prior propulsion control system (PCT/EP89/00953) and to a curve recognition procedure in the context of an antilock control system (DE-OS 37 39 558). A process for steering control is proposed in DE-OS 39 30 445.
The causes of the vehicle movements are essentially
acceleration and/or braking operations, PA0 steering operations and/or PA0 road surface unevennesses.
Important measured quantities representing the travel dynamics, particularly the transverse dynamics of the vehicle, and representing essential input variables of the control or regulation systems described above are the steering angle, or the transverse acceleration of the vehicle causally associated with the steering angle. Meant by steering angle is here the swing angle of the steerable wheels.
The steering angle, respectively the transverse acceleration of the vehicle, can be measured either "directly" by suitable sensors (steering angle sensors or acceleration sensors) or can be derived indirectly from other sensor signals. In view of minimizing the number of sensor systems, the "indirect" measuring methods should be given preference over the "direct" methods.
EP-OS 0353 995 describes a steering angle detector system where the steering angle is determined from the wheel RPM, or wheel frequencies, which differ in steering operations.
Exactly the maximally accurate determination of the transverse movements of a vehicle, for instance of the transverse acceleration, is of major importance for an optimum design of a chassis system and/or steering system.
It is known to provide a system for evaluation of wheel speed signals where the wheel speed difference is determined at minimal components expense. Moreover, it is proposed in such a system to determine the transverse acceleration of the vehicle in proportion to the vehicle speed and to the wheel speed difference. This has been proved as not being optimal.
The problem underlying the present invention is to determine a signal based on the wheel speed differences, which signal optimally represents the transverse movement of the vehicle, especially the transverse acceleration.